A motorist drives north for 30 min at `85km//h` and then stops for 15 min. He continues travelling north and covers 130 km in 2hours. What is his total displacement and average velocity?

Explanation

In first part:
Velocity, `v_1`=85 kmph
Time `t_1` =30 min
Distance travelled, `s_1=v_1t_1`
`=85times30/60=42.5km`
In second part: ,
Distance travelled , `s_2=0`,
Time `t_2`=15.0 min .
In third part:
Distance travelled, `s_3`=130 km,
Time ,`t_3`=120 min=2hours
a) Total distance of the motorist ,
`s=s_1+s_2+s_3=42.5+0+130=172.5km`
Total time travelled,
`t=t_1+t_2+t_3=30+15+120`
= 165 minutes
=2 hrs 45 minutes
`=2 3/4hrs.=11/4hrs.`
`therefore` Average velocity ,
`v_(avg)=(t otal displacement)/(t otal time)`
`172.5/((11//4))=62.7kmph`